Method for laser drilling fluid ports in multiple layers

ABSTRACT

A method includes attaching multiple layers to a back side of at least a portion of a fluid dispensing subassembly having at least one inlet port to form a fluid dispensing assembly, aligning a laser to a region of the fluid dispensing assembly, the region corresponding to the inlet port, and forming at least one hole in the region using a laser, the hole completing a path through the layers to the inlet port. A fluid dispensing assembly has a fluid dispensing subassembly having at least one inlet port, a fluid manifold having at least one outlet, at least two layers between the fluid dispensing subassembly and the manifold, and a fluid path in the at least two layers between the outlet and the inlet port, the fluid path having smooth walls and substantially uniform width.

BACKGROUND

Fluid dispensing assemblies generally include structures to take thefluid into the assembly or store it locally, route it to the appropriateoutput port, an actuator to selectively cause the fluid to exit theoutput port, and control circuit to control the selection and activationof the actuator. In some instances, the structures to route the ink tothe output port and structures upon which the actuators operate may becontained in a fluid dispensing subassembly.

One such fluid dispensing assembly consists of a print head, either forliquid ink or solid inks that are melted. It is generally helpful tohave a specific example to understand aspects of the discussion, but nolimitation to a print head is intended or should be implied. In theprint head example, the fluid dispensing subassembly typically consistsof series of metal plates, brazed or otherwise bonded together. Forpurposes of the discussion here, the jet stack will be considered toconsist of at least the membrane upon which the actuators operate, atleast one ‘body’ plate, the term ‘body’ applying to any plate betweenthe membrane and the nozzle plate, and the nozzle plate that containsthe exit ports.

In some instances, print heads include the ink manifolds that store anddispense the ink local to the jet stack. To achieve high density, it isadvantageous to remove these internal manifolds. The fluid dispensingassembly still requires some means to transfer ink from an ink reservoirto the output ports.

Ideally, this transfer would occur through a single port for each nozzlein the nozzle plate, for the printhead example, or more generally foreach output port. This results in a large number of ‘vertical’ portsthat must pass through multiple layers and maintain alignment. Thelayers may include the diaphragm or other structure upon which theactuator operates, between the actuators, through any standoffs orinsulators, a circuit board for the control circuitry and any heatersneeded, such as in solid ink printers. The small dimensions of theseinlets make it very difficult to assemble these layers withoutmisalignment, and to maintain uniform fluid characteristics in thepresence of any misalignment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a fluid dispensing assembly having individualjet inlets.

FIG. 2 shows a more detailed example of a fluid dispensing assemblyhaving individual jet inlets.

FIG. 3 shows an embodiment of a fluid dispensing assembly able to havethe inlets formed after assembly.

FIG. 4 shows an embodiment of a fluid dispensing assembly undergoinginlet formation.

FIG. 5 shows an alternative embodiment of a fluid dispensing assemblyundergoing inlet formation.

FIG. 6 shows an embodiment of a completed fluid dispensing assembly.

FIG. 7 shows an embodiment of a system for forming inlets.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Some fluid dispensing assemblies include a local fluid supply and afluid dispensing subassembly. The local fluid supply may reside in oneor more reservoir chamber or chambers within the fluid dispensingassembly. A print head serves as an example of a fluid dispensingassembly, with a jet stack acting as a fluid dispensing subassembly aswill be discussed in more detail later.

The term printer as used here applied to any type of drop-on-demandejector system in which drops of fluid are forced through one aperturein response to actuation of some sort of transducer. This includesprinters, such as thermal ink jet printers, print heads used inapplications such as organic electronic circuit fabrication, bioassays,three-dimensional structure building systems, etc. The term ‘printhead’is not intended to only apply to printers and no such limitation shouldbe implied. The jet stack resides within the print head of a printer,with the term printer including the examples above.

FIG. 1 shows one example of a fluid dispensing assembly. In thisinstance, for ease of discussion, the fluid dispensing assembly is aprint head. The print head 10 has a circuit board 12, through which theink from the manifold 13 travels to reach the fluid dispensingsubassembly 14. In this instance, the fluid dispensing subassembly wouldconsist of the jet stack of the print head.

A fluid dispensing subassembly may be viewed as having severalcomponents. First, the driver component may consist of the transducer,such as a piezoelectric transducer 21, that causes the fluid to exit thesubassembly, the diaphragm 28 upon which the transducer operates, andthe body plate 29 or plates that form the pressure chamber. Second, aninlet component consists of the port hole 24 the path into the jet stackthat directs the fluid from the manifold toward the pressure chamber.Next, the outlet component directs the fluid from the pressure chamberto the aperture or nozzle 25. Finally, the aperture dispenses fluid outof the printhead.

In operation, a signal to dispense fluid from a particular nozzle isreceived, such as through circuit trace 16. This signal is thentransmitted through the contact pad and conductive adhesive 18 to thetransducer 21 in the transducer layer 22. When the transducer operates,it presses against the diaphragm 28, which then causes the fluid to beejected through the nozzle 25 onto a print substrate or surface.

Several layers of structures exist between the jet stack and the circuitboard. The layer 22 is the transducer layer, which may be a layer ofindividual transducers 21, such as piezoelectric transducers, alignedwith each nozzle in the jet stack. Similarly, the regions between thetransducers must also align with the ink inlets 24 through the circuitboard 12, as do the existing holes in the diaphragm. This region 26 isshown in more detail in FIG. 2.

In FIG. 2, the ink inlet 24 is shown as it passes through the circuitboard 12. The standoff 20 and polymer in the transducer layer 22 musthave ink port holes 30 and 32 aligned with the ink inlet 24 and theopening 27 in the diaphragm 28.

This gives rise to several problems. For example, higher quality printsrequire a high density of jets in the jet stack. To provide these jetswith the necessary ink requires a high number of inlets that musttraverse several layers in the print head. Each of these inlets musthave precise alignment to ensure uniform fluid flow across all the jets.Non-uniformities can affect drop size and speed, which in turn mayresult in lower quality prints, as well as pressure and fluidfluctuations in the print head. In addition, these tight tolerances foralignment increase the cost of manufacture.

It is possible to alleviate these issues by assembling the layers on theback of the jet stack prior to forming the holes for the ink inlets.Once the layers are assembled, the holes could then be formed throughall of the layers. In order to accomplish this, the layers would need tobe ‘drillable’ or able to have holes formed in them. One possibility isto form the various layers out of polymers, with any critical componentswithin the polymers laid out to avoid regions where holes would bedrilled, but with more relaxed tolerances.

FIG. 3 shows a portion of an assembled print head 30 that has not yetundergone formation of the ink inlets. The external manifold is notshown. The jet stack 34 would interface with the remaining layersthrough the transducer layer 42. The jet stack or fluid dispensingsubassembly would have inlet ports 45 to allow the ink to enter the jetstack. As will be discussed in more detail later, the polymer layer mayhave some advantages during hole formation. The transducer layer 42would need to align such that the transducers make contact with theconductive adhesive such as 38 in the regions of the standoff 40, butwould not require the alignment precision required for the ink inlets.Generally, the transducers will have some sort of interstitial material,such as a polymer cured epoxy or polyimide, between them to planarizethe transducer layer.

Similarly, the stand off 40, possibly made of acrylic adhesive, wouldhave pre-cut holes to line up with the transducers, but again, thetolerances are much more relaxed than if they had to align a highdensity of very small holes for the ink inlets. The standoff will alsogenerally consist of a polymer layer. Further, layers of adhesive areused to attach the layers to the fluid dispensing subassembly and toeach other. These adhesives may be cured prior to formation of theholes. However, the layers could be bonded together without full curingof the adhesives. The full cure of the adhesives could take place afterthe ink inlets are formed.

Use of a flexible circuit substrate 32 may have advantages, althoughrigid circuit substrates may be used. Flexible circuit substrates, alsoreferred to as flex circuits, will generally consist of circuit tracesand passive components on the surface of a polymer substrate such aspolyimide. As mentioned previously, the circuit traces may be laid outor positioned such that they will avoid any regions that may be drilled.

The print head portion of FIG. 3 also shows a heater layer 46. Forsolid, or phase-change ink printers, the ink path is generally heated tomaintain the ink in its liquid state. A heater layer made of, forinstance, a polyimide substrate with metal heater traces on one or bothsurfaces may then exist as part of the print head. The heater layerwould be arranged such that any metal traces would avoid the regions tobe drilled. It must be noted that the aspects of the invention describedhere are not limited to phase-change ink printers and should not beinterpreted as such. The heater layer is therefore optional, but doesdemonstrate that it is possible to include such structures and stillreceive the benefits of the embodiments set out here.

Similarly, while it is shown here to demonstrate that several additionallayers can still use the aspects of the invention, the manifold attachadhesive 44 is also optional. This would be the adhesive that allows theink manifold, such as the one shown in FIG. 1, to be attached to theassembled print head structures discussed above. The adhesive layers maycome from a number of classes of adhesive including acrylic, epoxy,phenolic, or silicone or combinations thereof. However, the holes forthe ink inlets would generally be formed prior to attaching themanifold.

Once the portion of the print head in FIG. 3 is assembled, the holes canbe formed. FIG. 4 shows one embodiment of a method to form the holes bylaser. The laser beams such as 50 would drill through or ablate thelayers between the manifold attach adhesive and the jet stack. The lasercan be aligned to the regions of the print head corresponding to the inkstructures in the jet stack using standard vision alignment systems. Theholes could then be cut with tight control over the size and shape,guaranteeing the uniformity of the fluid characteristics across themultiple jets of the print head.

In the embodiment of FIG. 4, the holes are drilled from the ‘manifold’side of the portion of the print head assembly. This is the side of theprint head where the manifold will reside. In one embodiment, the inkinlets are formed with the fluid dispensing subassembly or jet stackfully intact, including the nozzle plate 48.

FIG. 5 shows an embodiment of a hole formation process from the nozzleplate or fluid dispensing subassembly side of the print head, where thenozzle plate itself is not attached to the rest of the fluid dispensingsubassembly or jet stack. The laser or other hole forming apparatuswould form the holes through the ink paths in the fluid dispensingsubassembly that connect to the manifold. The nozzle plate would then bealigned to the outlets of the fluid dispensing subassembly and attachedafter the holes were formed.

However the holes are formed, whether by laser cutting, ablation orother process, the completed portion of the print head without themanifold would appear something like that shown in FIG. 6. As can beseen, the ink inlets 52 have smooth walls and generally uniformcircumference or width. The inlet through the polymer layers can besmaller than the ink inlet in the ink dispensing subassembly. Whencompared to the alignments of FIG. 1, it can be seen that the featuresare perfectly aligned laterally. As mentioned above, this alleviatessome of the issues with non-uniform fluid flow and resulting imageartifacts and system operation issues that result from that non-uniformflow.

There are a several methods for forming the holes. Specific selection ofa laser source for hole formation will depend on the composition andphysical properties of the material being processed, the thickness ofeach of the several layers, the overall thickness of the polymer layers,the spatial resolution required, the desired surface quality, andeconomic considerations such as power consumption, equipment cost,maintenance cost, and processing speed. The range of laser possibilitiesinclude, but are not limited to, excimer, CO₂, diode pumped solid state,copper vapor and fiber lasers. Both aperture imaging and scanned lasercutting can be used depending upon several factors.

FIG. 7 shows a system 60 using an image wise ablation method. The lasersource 62 emits a laser emission 64, which is processed through avariable attenuator 66 and beam shaping stage 68. The laser passesthrough a mask 70 that transmits light in the pattern of the cut (notshown). The patterned emission is directed by mirror 72 through anappropriate lens 74, which images the mask onto the print headassemblies such as 30 as shown in FIGS. 3-5. The imaged laser pattern isaligned to the desired location of the ink port holes using visionalignment or other means of registration.

Each of the laser source 62, variable attenuator 66, mask 70 and cuttingstage 78 is operably connected to a suitable controller 80. The laser isused to illuminate the mask and forms a laser light image of the area tobe cut on the print head assembly. An appropriate number of pulses fromthe laser source can remove, by an ablation process, the unwantedmaterial. A modification of the imaging method may also scan somecombination of the laser beam illuminator, the mask, and the rawmaterial. Each of these methods is encompassed by the present invention,as well as variants thereof that will be apparent to one skilled in theart based on the present disclosure.

In this system, a number of port holes for the ink inlets could beformed simultaneously by the imaged apertures illuminated by the laser.Additional ink ports could be formed by a step and repeat process wherethe print head is sequentially moved in a precise manner to a newlocation and the laser activated for each of these locations.

In another embodiment, the laser source 62 could be a diode pumped solidstate laser and the laser would be galvanometer scanned to cut each inkport sequentially. All of the ink ports within the field of view of thescanner could be cut sequentially. If the part were larger than thefield of view, the part could be moved until all of the port holes havebeen created

It will be appreciated that several of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations, or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

1. A method, comprising: attaching multiple layers to a back side of atleast a portion of a fluid dispensing subassembly having at least oneinlet port to form a fluid dispensing assembly, wherein attachingmultiple layers includes applying a manifold attach adhesive to a toplayer of the multiple layers; aligning a laser to a region of the fluiddispensing assembly, the region corresponding to the inlet port; andforming at least one hole in the region using a laser, the holecompleting a path through the layers to the inlet port.
 2. The method ofclaim 1, wherein attaching multiple layers includes attaching anactuator layer having a polymer in at least one space between actuatorsin the actuator layer, the space corresponding to the inlet port.
 3. Themethod of claim 2, wherein the space between the actuators has aninterstitial polymer, the polymer being one of epoxy, acrylic, phenolicor silicone or a combination thereof.
 4. The method of claim 1, whereinattaching multiple layers includes attaching a heater layer, the heaterlayer being arranged so any metal traces avoid the region.
 5. The methodof claim 1, wherein attaching multiple layers includes attaching anelectronic circuit, the electronic circuit being arranged so any metaltraces do not fully or partially cover the region.
 6. The method ofclaim 1, wherein attaching multiple layers includes using an adhesive toattach at least one layer and curing the adhesives used between thelayers prior to forming at least one hole.
 7. The method of claim 1,wherein attaching multiple layers includes leaving at least one adhesivelayer uncured.
 8. The method of claim 1, wherein aligning the lasercomprises aligning the laser to a manifold side of the fluid dispensingassembly, and the fluid dispensing subassembly comprises a completefluid dispensing subassembly.
 9. The method of claim 1, wherein formingat least one hole comprising drilling from a manifold side.
 10. Themethod of claim 1, wherein aligning the laser comprises aligning thelaser to the inlet port on a portion of the fluid dispensingsubassembly.
 11. The method of claim 1, wherein forming at least onehole comprises drilling the hole from the fluid dispensing subassemblyside through the multiple layers.
 12. The method of claim 11, furthercomprising attaching a nozzle plate onto the fluid dispensingsubassembly after drilling.
 13. The method of claim 1, wherein formingat least one hole further comprises forming multiple holessimultaneously.
 14. The method of claim 1, further comprising repeatingthe aligning and forming in a step and repeat fashion to form an arrayof holes corresponding to an array of output ports in the fluiddispensing subassembly.
 15. The method of claim 1, wherein forming atleast one hole using a laser further comprises using one of an excimerlaser, a carbon dioxide laser, a diode pumped solid state laser, acopper vapor laser, or a fiber laser.
 16. The method of claim 1, whereinforming at least one hole using a laser further comprises using one ofan aperture imaging laser or a scanned laser.